1. Field of the Invention
The present invention relates to a reverberation imparting apparatus which simulates acoustic characteristics of the sound-field space having a relatively long reverberation time.
2. Prior Art
As the method of imparting reverberation to audio signals, there is provided a reverberation imparting method which utilizes a so-called reflected-sound-synthesis system. This method uses a memory, such as a read-only memory (i.e., ROM), which stores a string of sampling data representative of reflected sounds in advance. The reflected sounds are picked up (i.e., an impulse response is measured) when an impulse sound is artificially produced in the certain sound-field space such as the concert hall or auditorium. Then, the arithmetic convolution is performed using a string of sampling data, which are stored in the ROM, on another string of sampling data representative of the audio signals. Thus, it is possible to obtain the audio signals to which the reverberation is imparted. This method is advantageous in that by merely storing a string of sampling data representative of the reflected sounds, a variety of reverberation effects, corresponding to a variety of sound-field spaces, can be imparted to the audio signals.
Meanwhile, when an impulse sound is produced in a certain kind of sound-field space such as the church, the reverberation sounds are sounded for a relatively long time. When synthesizing such reverberation sounds by the above-mentioned reverberation imparting method utilizing the reflected-sound-synthesis system, the arithmetic convolution should be performed, using a string of sampling data representative of the reverberation sounds having a relatively long reverberation time, on a string of sampling data representative of the audio signal which also have a relatively long sounding time. Such arithmetic convolution requires a high-performance digital signal processor (i.e., DSP) having a large tap number. In other words, it is necessary to provide a DSP which is capable of performing the arithmetic convolution, using the addition and multiplication, many times in each sampling period. In order to embody the DSP, having a large tap number, it is necessary to provide a plenty of multipliers inside of the DSP. Or, it is necessary to increase an execution speed of the DSP such that the convolution processing, using the addition and multiplication, can be performed many times in one sampling period. Because of the reasons described above, it is difficult for the conventional technology to impart the reverberation sounds, having a long reverberation time, to the audio signals.